"Sexual attraction is a response to stimuli - that can be based on any number of things for example waist to hip ratio, certain behaviours, or breast size," Dr Timmins says.

"If you have a trans woman who transitions very early on, she may be physically identical to a cis woman."

A "cis woman" or "cisgendered" person is someone whose gender identity matches the one they were born with.

"There are hormonal sweet spots where trans women can transition and be effectively indistinguishable at a certain level from cisgendered women," Dr Timmins says. "So being unwilling to date on the basis of someone being trans, rather than on the basis of individual stimuli is something I would personally call transphobic."

"This is a philosophical rather than empirical discussion because their is not a lot of nuanced research into this area yet.

"Grouping all transgender women as the same and all cis gender women as the same is effectively prejudice," Dr Timmins says.